Method of manipulating and forming material at temperatures between solidus and liquidus

ABSTRACT

A method of manipulating and forming material where the material is a metal blank. The blank is inserted into an electromagnetic field that keeps it in levitation and heats it up to the temperature between solid state and liquid state. Temperature is measured by infrared thermometer. After the blank reaches the required temperature it is formed to the desired shape by external force. The temperature changes during the forming phase and this change can be controlled or uncontrolled. Forming of levitated blank is done by changing position of levitation device by inserting the blank between forming tools or levitated blank stays in place and forming tools move towards it and then the forming takes place.

FIELD OF THE INVENTION

The invention generally pertains to manipulation and forming of metal materials at temperatures between solid and liquid phase. It falls into the field of altering the physical properties of a material during heat treatment or after it.

DESCRIPTION OF THE PRIOR ART

By forming material at temperatures between solid and liquid. states (thixoforming) it is possible to obtain material structures that are difficult to achieve by other methods of forming. The principle of this process consists in forming material at a temperature at which part of the material is in liquid state and part in solid state. This happens only at a narrow temperature interval and this interval depends OD the material. In order to perform this forming it is necessary to heat the material to a precise and uniformly distributed temperature.

The following procedure is currently used. Material is heated to the required temperature in a conventional furnace or by induction heating. It must stay at this temperature for some time to achieve uniform temperature distribution. Than it is removed from the furnace by tongs or by a manipulator and inserted into a liming die where it is formed by force into a desired shape. This procedure has some disadvantages. The biggest one is that the material comes into contact with several objects during processing so it disturbs the uniformity of temperature distribution. It especially applies to the process of removing material from the furnace and its insertion into a die. Gripping the material cools down the surface of contact and it can even distort the shape of the material, because it is in semisolid state. The material also has a tendency to stick to the grip, which complicates subsequent insertion into the die. As a result the material can be incorrectly inserted into the die and consequently improperly formed.

Another problem is manipulation with high volumes of semisolid material because it has a tendency to come apart clue to its own weight. Also very small volumes of material are difficult to handle and disturbance of temperature distribution uniformity is even higher. All of these problems are usually solved by various modifications of working procedures and manipulating devices, nevertheless, material still comes into contact with other objects during processing.

Oxidation of material when transported from furnace to the die is another problem. It can be minimized by use of an inert atmosphere but its implementation on the route between furnace and die is difficult.

SUMMARY OF THE INVENTION

The presented invention discloses a new method for manipulating and forming material at temperatures between solid and liquid states. It is suitable for metal blanks.

The principle of this method consists in heating and forming the material in electromagnetic levitation, where the material is free of any contact with surrounding objects. Temperature measurement is also contact-less so the die is the only thing the material comes into contact with during processing. It eliminates a lot of problems, especially the problem with disturbed uniformity of temperature distribution and material deformation due to contact with handling tools. Because the material is formed directly in the heating/levitating device, there is no drop of temperature due to transportation from furnace to die. It also simplifies usage of an inert atmosphere for corrosion elimination.

The proposed invention expands the application field of thixoforming to the area of forming very small parts, which are difficult to form by conventional methods. It can be fully automated and is suitable for serial production.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A blank made of 100Cr6 steel composed of 1% of C, 0.25% of Si, 0.35% of Mo and 1.5% of Cr is inserted into the electromagnetic field of a levitation/melting coil. The electromagnetic field heats the material and keeps it in levitation. The temperature of the blank is measured by infrared thermometer using two-color ratio method to eliminate the influence of the blank movement in the electromagnetic field.

Forming is performed after reaching a temperature of 1380 to 1420° C., when 10 to 40% of material is in liquid state. Forming is done by a pair of dies that moves towards the levitated material from above and from below through the center of the levitation coil. The rate of temperature change of the material during the forming phase is controlled by cooling of dies to room temperature. 

1. Method of manipulating and forming material at temperatures between solid and liquid states where the material is a metal blank where the method is characterized by the fact that the blank is inserted into an electromagnetic field of a levitation device that keeps it in levitation and heats it up to the required temperature, temperature is measured by contact-less thermometer, after blank reaches the temperature between solid state and liquid state it is formed to desired shape by external force and at the same time con rolled or uncontrolled change of blank temperature occurs.
 2. Forming of levitated blank according to claim 1 is done by changing position of levitation device by inserting the blank between forming tools.
 3. Forming of levitated blank according to claim 1 is carried out so that the levitated blank stays in place and forming tools move towards it and then forming occurs. 